Links to the different topics

Introduction

Currently there are five manufacturers of over 300 ton capacity haul trucks for mining applications in the world. Caterpillar and Terex Unit Rig as American companies, Liebherr with headquarters in Germany and two Japanese companies, Komatsu and Hitachi.Despite the international constellation in the mining truck market, all five manufacturers have assembly plants in the United States as the main market for off-highway haulers is North America.My LEGO model represents the first version of Liebherrs top of the range model, the T 282 with a nominal payload capacity of 360 short tons which equal about 320 metric tons.Trucks of this size class are usually loaded by mining rope shovels like P&Hs 4100 series or Bucyrus' 495 series.Inspiration for this model came after I got another two Technic wheels of the size 24 x 43 with yellow rims so that I now have six of them. On my truck they represent the 55/80R63 tires of the real machine which feature a diameter of nearly four meters.Although the standard color scheme of Liebherr trucks is white, I opted for the yellow version which in reality was applied on an early machine. The main reasons for this decision were not only the wheels but also the fact that LEGO Pneumatic cylinders are only available in yellow.Thanks to the relatively small size of the model - the scale is about 1 / 50 - it was much easier to transport the truck to a nearby quary to take the pictures you can see on this page. (Read about problems with transportation and taking pictures of large models on the Mountaineer page.)

Dump Body

The most important part on every mining truck is the dump body. My model features a standard body which is used to transport overburden and rocks. If the truck is used to haul coal, dump bodys with bigger capacities and tailgates are available.To provide a smooth surface, not only the side walls of the dump box are built using basic bricks. The floor and the back wall form a 90 degree angle and are built with 1 x X bricks as well. Slope bricks on the edges between the floor plate and the side walls give the dump body a realistic look and add to an optimal material flow while dumping. Fins on the outer sides of the dump box add strength and improve the construction optically.A protective roof prevents the drivers cab and the electrical installations on the engine hood from being smashed by rocks while loading the truck.Dumping works by means of two old style single acting Pneumatic cylinders. I used the ones with the longer stroke to achieve an adequate dumping angle and to be able to still apply a force big enough to dump the box full of LEGO bricks.When chosing the single acting cylinders, I thought that lowering the dump body would be no problem as gravity solves this problem after pressure in the cylinders is released. I was wrong. Because the center of gravity of the dump box nearly reaches a position almost vertical above the hinges when fully tipped, the resulting lowering momentum is too small to overcome the friction in the dump cylinders. Therefore the dump body stayed in its position after releasing air pressure and I had to apply the hand of god to get the body back in its original position.The solution to this problem consists of a rubber belt that is attached to the dump body and the truck frame. It starts to apply a force opposed to the dumping force when the cylinders are extended by about half of their stroke. The force gets bigger while increasing the tipping angle and finally is big enough to drive the dump box back to its horizontal position when pressure on the dumping cylinders is released. With this solution it is still possible to dump a heaped body of basic bricks.

Steering Mechanism

While the real T 282 uses hydraulic steering cylinders, my model features pneumatic steering with the small double acting LEGO cylinders.There is one cylinder per side, each connected with the piston rod to the steering arm and with the opposing end to the main frame. To achieve a movement in unison, the air inlet on the piston side of the left cylinder is connected to the air inlet on the side of the piston rod of the right cylinder and vice versa.Because the front wheels feature independent suspension, I had to build a mechanism that allows to compensate the vertical movement of the steering arms relative to the truck frame. As there is no possibility to use spherical joints on the steering cylinders and still achieve a compact mechanism, I found another solution. There is a vertical Technic axle attached to each steering arm which can glide up and downwards in the eye of the piston rod.First tests showed that the compensation of the vertical wheel movements worked well but the left and right wheel never steered in unison. Therefore the two steering arms are linked to each other by means of a Flex System cable that attaches to the steering arms on their upper sides while the Pneumatic cylinders attach to the lower sides. The flexible cable is guided in a tube that crosses the truck frame from side to side.Compared to a mechanical solution with rack and pinion the pneumatic version is more compact and has a much more realistic look. On the other hand steering is not that accurate as there is no defined center position and therefore the model tends to steer either to the left or to the right.

Suspension

There are many different suspension philosophies for the front wheels on the different off-highway hauler brands. While Caterpillar and Komatsu for example use nitrogen/oil struts where the wheel is directly mounted to the piston rod, Terex Unit Rig trucks feature a rigid axle concept.Liebherr mining trucks use a dual parallel control arm arrangement which allows for an independent suspension of the left and the right front wheel. My model features the same arrangement using four stud long liftarms to represent the triangular control arms of the real machine.While on the real T 282 haul road shocks are absorbed with nitrogen/oil struts that attach to the upper control arm and the truck frame, my model uses small spring shock absorbers. Yellow LEGO shock absorbers would fit best as they would not only match with the color scheme of the model but also feature the strongest springs. I used grey ones because I don't have any yellow ones. Therefore additional rubber belts are used to stiffen the suspension as the weight of the front part of the truck is quite heavy. The rubber belts attach to the lower control arms and to a Technic pin between the two steering cylinders.Rear axles on mining trucks are usually rigid axles. While Caterpillar haulers feature a mechanical drive and therefore the axle houses a differential gear, all the other manufacturers use electric wheel motors which are mounted to the axle housing. Drive on my model is a compromise between the two mentioned concepts. A geared 9V motor drives via a worm gear the 24 tooth gear on the differential cage. Therefore my model features electromechanical drive.The whole motor-differential assembly forms the rigid rear axle which is connected to the frame by pins to allow an up and down movement. Instead of shock absorbers two rubber belts are used to realize a working suspension. They attach to the drive motor and to a cross member on the truck frame. Depending on the strength of the rubber belts a suspension can be realized that matches to the gross vehicle weight.

Details

Besides the functions discussed above on a real mining truck there are many more components used for a working machine. Although they have only a static function on my model I tried to copy them as well.First important detail is the engine. There is a 16 cylinder V-engine located behind the massive cooling unit. It represents either a Detroit Diesel / MTU 16V4000 or a Cummins QSK60 on the real truck. Both engines are available with a rating of 2750 horsepower.The compressors on the engine need air which is drawn through air intake pipes at whose ends air filter units are mounted. These suction filters can be found on my model below the right and left corner of the control deck besides the access ladders.The diesel electric drive system of the real mining truck needs static DC/AC converters which are located besides the left-mounted drivers cab under the protective roof. These components, toghether with a heat exchanger can be found at the corresponding place on my model as well.Further details include headlights, rear and position lights, fuel tanks, access ladders, railings, rear view mirrors, green-orange-red light arrays to communicate with the shovel operator and fire extinguishers. Finally a set of self made stickers give the model the finishing touch. There are manufacturer logos and model designation plates at various places on the truck and the dump body.

Remote Control

To prevent the model from being just a static display I built a remote control unit to access drive, steering and dumping functions. It consists of a hand held box that contains different modules.First of all there is the power source which makes use of a 9V battery box containing six AA batteries. It delivers power for the drive motor and an air compressor. The forward-stop-backwards movement can be controlled with a pole reverser switch while the air compressor is controlled by an automatic pressure switch.When switching power on, the air compressor which consists of two geared 9V motors driving a two cylinder air pump builds up air pressure. When pressure rises a small Pneumatic cylinder is forced to extend against the force of two rubber belts and sets a switch to the off position cutting the power for the air compressor. Pressure falls when either the steering or the dump mechanism is actuated. Due to the rubber belts the Pneumatic cylinder is forced to retract and thus switches power for the compressor on again.Air pressure is distributed to two valves, one for steering and one for dumping. From the steering valve two tubes lead to the model and connect there to the tubing that distributes the air to the two steering cylinders. Only one tube is used to connect the dumping valve to the dumping cylinders on the model as the latter ones are single acting.Therefore the umbilical connecting the remote control unit and the T 282 consists of three Pneumatic tubes and one electric cable. The length is about 1.2 meters giving an adequate working range.When the model is operated indoor a 9V train speed regulator that plugs to the mains can be used to power the electric functions. To realize this, there is a cable reserve in the control unit that can be connected to the speed regulator.Controlling such a model is a lot of fun. Driving around and steering the model works fine. And a bucket full of LEGO bricks can be dumped easily.